To my knowledge, that may not mean anything. Drivers can postpone/defer/queue the actual processing of the GL calls until their effect must be known, which is at glfwSwapBuffers() or glFinish() or other calls such as glReadPixels() when you are reading the backbuffer which you previously rendered to. In addition, the GPU will start processing the GL calls and will do this asynchornously to your CPU/host program. Only at glfwSwapBuffers() and glFinish() will the GPU and CPU synchronize (and in most cases the CPU wait for the GPU to finish).
If you want to know how long calls take on the GPU, measure the GPU time via timer query objects.